/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.flink.runtime.rest.handler.taskmanager;

import org.apache.flink.api.common.time.Time;
import org.apache.flink.runtime.resourcemanager.ResourceManager;
import org.apache.flink.runtime.resourcemanager.ResourceManagerGateway;
import org.apache.flink.runtime.rest.handler.AbstractRestHandler;
import org.apache.flink.runtime.rest.handler.HandlerRequest;
import org.apache.flink.runtime.rest.handler.RestHandlerException;
import org.apache.flink.runtime.rest.messages.MessageHeaders;
import org.apache.flink.runtime.rest.messages.MessageParameters;
import org.apache.flink.runtime.rest.messages.RequestBody;
import org.apache.flink.runtime.rest.messages.ResponseBody;
import org.apache.flink.runtime.webmonitor.RestfulGateway;
import org.apache.flink.runtime.webmonitor.retriever.GatewayRetriever;
import org.apache.flink.util.Preconditions;

import org.apache.flink.shaded.netty4.io.netty.handler.codec.http.HttpResponseStatus;

import javax.annotation.Nonnull;

import java.util.Map;
import java.util.Optional;
import java.util.concurrent.CompletableFuture;

/**
 * Base class for TaskManager related REST handler which need access to the {@link ResourceManager}.
 *
 * @param <T> type of the {@link RestfulGateway}
 * @param <R> request type
 * @param <P> response type
 * @param <M> message parameters type
 */
abstract class AbstractTaskManagerHandler<T extends RestfulGateway, R extends RequestBody, P extends ResponseBody, M extends MessageParameters> extends AbstractRestHandler<T, R, P, M> {

	private final GatewayRetriever<ResourceManagerGateway> resourceManagerGatewayRetriever;

	protected AbstractTaskManagerHandler(
			GatewayRetriever<? extends T> leaderRetriever,
			Time timeout,
			Map<String, String> responseHeaders,
			MessageHeaders<R, P, M> messageHeaders,
			GatewayRetriever<ResourceManagerGateway> resourceManagerGatewayRetriever) {
		super(leaderRetriever, timeout, responseHeaders, messageHeaders);

		this.resourceManagerGatewayRetriever = Preconditions.checkNotNull(resourceManagerGatewayRetriever);
	}

	@Override
	protected CompletableFuture<P> handleRequest(@Nonnull HandlerRequest<R, M> request, @Nonnull T gateway) throws RestHandlerException {
		Optional<ResourceManagerGateway> resourceManagerGatewayOptional = resourceManagerGatewayRetriever.getNow();

		ResourceManagerGateway resourceManagerGateway = resourceManagerGatewayOptional.orElseThrow(
			() -> new RestHandlerException("Cannot connect to ResourceManager right now. Please try to refresh.", HttpResponseStatus.NOT_FOUND));

		return handleRequest(request, resourceManagerGateway);
	}

	protected abstract CompletableFuture<P> handleRequest(@Nonnull HandlerRequest<R, M> request, @Nonnull ResourceManagerGateway gateway) throws RestHandlerException;
}
